123results about How to "Small F number" patented technology

Disclosed is an imaging lens having a small F-number, high resolution, a sufficiently wide angle of view, and a small size.

An imaging lens includes: a first lens with a meniscus shape having a concave surface facing an object side; a second positive lens; a third negative lens with a meniscus shape having a convex surface facing an image side; and a fourth lens having a convex surface facing the object side. The first to fourth lenses are arranged in this order from the object side. The imaging lens satisfies the following conditional expression:

0.25<D/f<4.0

• • (where D indicates the distance between the first lens and the second lens on the optical axis and f indicates the focal length of the entire system).

Disclosed is an imaging lens having a small F-number, high resolution, a sufficiently wide angle of view, and a small size.

An imaging lens includes: a first lens with a meniscus shape having a concave surface facing an object side; a second positive lens; a third negative lens with a meniscus shape having a convex surface facing an image side; and a fourth negative lens. The first to fourth lenses are arranged in this order from the object side. The imaging lens is configured such that a normal line of an object-side surface of the fourth lens at a point where the outermost light beam of an on-axis light flux passes intersects the optical axis on the image side of the object-side surface.

A slim lens assembly includes a first lens, a second lens, a third lens, a fourth lens and a fifth lens, all of which are arranged in sequence from an object side to an image side along an optical axis. The first lens is a convex-concave lens with negative refractive power and includes a convex surface facing the object side and a concave surface facing the image side. The second lens is with positive refractive power. The third lens is a biconcave lens with negative refractive power. The fourth lens is a biconvex lens with positive refractive power. The fifth lens is a convex-concave lens with negative refractive power and includes a convex surface facing the object side and a concave surface facing the image side.

Disclosed is an image pickup lens having the following disposed from an object side in the order listed below: a first lens having a negative power and a meniscus shape with a concave surface on an image side; a second lens having a positive power; a third lens having a negative power; a fourth lens having a positive power; a fifth lens having a positive power; and a sixth lens having a negative power and a meniscus shape with a concave surface on the object side. The image pickup lens satisfies Conditional Expression (1) given below when a focal length of the first lens is taken as f1 and a focal length of the second lens is taken as f2.

−3.0<f1/f2<−1.6  (1)

A variable magnification optical system includes a positive first lens group, a negative second lens group, a stop, a positive third lens group and a positive fourth lens group, which are in this order from an object side. The first lens group, the stop and the third lens group are fixed, but the second lens group and the fourth lens group move in an optical axis direction during magnification change. The fourth lens group has a focusing function. The third lens group includes at least an aspherical surface, and consists of, in the following order from the object side, a positive lens and a cemented lens of a positive lens and a double-concave lens cemented together. The variable magnification optical system satisfies a predetermined formula.

In constructing a lens for projection substantially consisting of seven lenses, and the reduction side of which is telecentric, a first-lens-group is composed of two lenses including at least one negative lens. A second-lens-group is composed of a positive second-group first-lens having a convex surface facing the magnification side, a negative second-group second-lens having a concave surface facing the magnification side, a positive second-group third-lens having a convex surface facing the reduction side, a positive second-group fourth-lens, and a positive second-group fifth-lens in this order from the magnification side. The formulas (A) and (B) are satisfied:

1.2≦Bf/f≦2.5  (A);

and

f23/f≦1.5  (B),

where

• • Bf is a back focus in air of an entire lens system,
  • f is the focal length of the entire lens system, and
  • f23 is the focal length of an air lens between a reduction-side surface of the second-group second-lens and a magnification-side surface of the second-group third-lens.

A lens for projection substantially consists of a negative first lens group, a positive second lens group and a positive third lens group in this order from a magnification side. A reduction side is telecentric, and a most magnification-side lens is an aspheric plastic lens. The third lens group consists of a negative front group and a positive rear group in this order from the magnification side with an air space therebetween. The front group consists of a negative lens and a positive lens in this order from the magnification side with an air space therebetween, and the air space being narrower than the air space between the front group and the rear group. Conditional formula (1): −0.7<fFG3/f<0.7 about front focus fFG3 of the third lens group and focal length f of an entire system is satisfied.

A negative first lens having a concave surface facing the reduction side of a lens for projection, a positive second lens having a convex surface facing the magnification side of the lens for projection, a negative third lens having a concave surface facing the magnification side, a positive fourth lens having a convex surface facing the reduction side, a positive fifth lens, and a positive sixth lens are arranged in this order from the magnification side, and the reduction side of the optical system is telecentric. Further, the following formula (A) is satisfied:

1.2≦Bf/f≦2.5  (A), where

Bf: back focus in air of the entire lens system of the lens for projection, and

f: focal length of the entire lens system.

A zoom lens for projection includes a negative first lens group, a positive second lens group, a positive third lens group, and a positive fourth lens group, which are arranged from the magnification side of the zoom lens in the order mentioned above. The first lens group and the fourth lens group are fixed during zooming, but the second lens group and the third lens group move on optical axis Z of the zoom lens toward the magnification side, based on an operation for operating the zoom lens from wide end to tele end, in such a manner that a distance between the second lens group and the third lens group changes. Further, the following formula (1) is satisfied:

17<F_G3/fw  (1), where

• • F_G3 focal length of the third lens group, and
  • fw: focal length of entire system at wide end.

The imaging lens consists of, in order from the object side, a first lens group having a positive refractive power, a second lens group, and a third lens group. In the second lens group, a first focus lens group having a negative refractive power is disposed to be closest to the object side, and a second focus lens group having a positive refractive power is disposed to be closest to the image side. During focusing, only the first and second focus lens groups move by changing the mutual spacing therebetween. The first lens group has two positive lenses and one negative lens. The first focus lens group consists of two or less lenses including a negative lens. Predetermined conditional expressions are satisfied.

A zoom lens consists of, in order from the object side, a positive first lens group, a negative second lens group, a negative third lens group, a negative fourth lens group, a positive fifth lens group, and a positive sixth lens group. The first lens group and the sixth lens group are fixed with respect to an image plane, and a distance between the first lens group and the second lens group increases, a distance between the second lens group and the third lens group changes, and a distance between the third lens group and the fourth lens group changes, and a distance between the fourth lens group and the fifth lens group changes, and a distance between the fifth lens group and the sixth lens group changes during magnification change from a wide angle end to a telephoto end.

A lens for projection substantially consists of a negative first-lens having a concave surface facing the reduction side, a positive second-lens having a convex surface facing the magnification side, a negative third-lens having a concave surface facing the magnification side, a positive fourth-lens having a convex surface facing the reduction side, and a positive fifth-lens, arranged in this order from the magnification side. Further, the following formulas (A) through (D) are satisfied:

1.2≦Bf/f≦2.5  (A);

−3.0≦f3F/f≦−0.8  (B);

1.4≦f5F/f5≦8.5  (C); and

1.0≦d12/f≦2.7  (D), where

• • Bf is a back focus,
  • f is the focal length of an entire lens system,
  • f3F is the focal length of a magnification-side surface of the third-lens,
  • f5F is the focal length of a magnification-side surface of the fifth-lens,
  • f5 is the focal length of the fifth-lens, and
  • d12 is an air space between the first-lens and the second-lens.